Next story in Space

NASA's New Horizons probe today (Jan. 15) began its six-month
approach to Pluto,
which will culminate with the first-ever close flyby of the dwarf
planet on July 14.

"We really are on Pluto's doorstep," New Horizons principal
investigator Alan Stern said last month during a news conference
at the annual fall meeting of the American Geophysical Union
(AGU) in San Francisco. [ Photos
from NASA's New Horizons Pluto Probe ]

The $700 million New Horizons
mission blasted off in January 2006 with the aim of lifting
the veil on Pluto. The dwarf planet has remained a mystery since
its 1930 discovery because it's so small and so far away. (On
average, Pluto orbits about 40 times farther from the sun than
Earth does.)

The piano-size spacecraft rocketed away from Earth at more than
36,000 mph (58,000 km/h), faster than any other probe. It has now
covered about 3 billion miles (4.8 billion kilometers) during its
nine-year journey through deep space.

"In a very real sense, this is the Everest of planetary
exploration," Stern said of New Horizons. "This mission
represents the closing of the first era of planetary
reconnaissance. We've made it to the farthest place, with the
fastest spacecraft ever launched."

New Horizons will use seven different science instruments to
study
Pluto and its five known moons. The mission's chief
objectives include mapping the surface composition and
temperature of Pluto and its largest moon, Charon; characterizing
the atmosphere of Pluto and the geology of Pluto and Charon; and
hunting for rings and additional satellites in the Pluto system.

In the 1990s, researchers began to realize that Pluto is not a
lonely misfit; rather, it's just one of many dwarf planets and
other icy denizens of the far-flung Kuiper
Belt, which lies beyond Neptune's orbit. So New Horizons'
observations should help researchers better understand an entire
class of solar system bodies, mission team members said.

"We are going to the archetypal Kuiper Belt planet," New Horizons
co-investigator William McKinnon, of Washington University in St.
Louis, said at the AGU news briefing. "This mission will
revolutionize our understanding of how the planets in the Kuiper
Belt work."

Small, icy worlds like Pluto are probably the most common type of
planet in the entire universe, McKinnon added.

Though New Horizons remains about 134 million miles (216 million
km) from Pluto, it has already begun taking the dwarf planet's
measure: The science-observation campaign officially began today,
marking the start of "Approach Phase 1."

Many of the images New Horizons gathers during this phase will be
used to keep the spacecraft on target toward Pluto, with the
first course-correction maneuver, if necessary, possibly
occurring as early as March. But some of the photos will be taken
for scientific purposes, Stern said, and New Horizons will also
characterize the Kuiper Belt environment using two different
plasma sensors and a dust-counting instrument.

The pace of scientific activity will really start picking up in
April, Stern added. And by mid-May, New Horizons will be close
enough to snap the best-ever images of Pluto. (The sharpest
photos of the dwarf planet to date were taken by NASA's
Hubble Space Telescope ; they show Pluto as a blur of pixels.)

It will only get more exciting from there. The most jaw-dropping
images will be captured on and around July 14, when New Horizons
zooms within about 6,000 miles (9,656 kilometers) of Pluto's
surface.

The closest-approach pictures will not all be available right
away, however. As a result of budget constraints, New Horizons
does not have an articulated high-gain antenna, meaning the
spacecraft must orient itself toward Earth to beam data home.

But New Horizons will of course be peering intently at Pluto
during and immediately after the flyby. While some images will
come down to mission control during this time, high-volume
transmission of closest-approach data likely won't begin until
early August, Stern said, and will continue for more than a year.

"From a scientific standpoint, this is going to look a lot like
an orbiter [mission]," he said. "The spacecraft is long gone from
Pluto, but new data is raining down every week, and every month,
for 16 months."

The Pluto flyby may not end New Horizons' scientific work in the
dark depths of the outer solar system: Stern and his team want to
send the probe on to
observe another Kuiper Belt object, and they've already
identified two good candidates. If NASA funds this extended
mission, New Horizons would reach its second and final target in
2019.